The Pebble-Bed Advanced High Temperature Reactor (PB-AHTR), a Fluoride Salt Cooled High Temperature Reactor (FHR)

Transcription

1 The Pebble-Bed Advanced High Temperature Reactor (PB-AHTR), a Fluoride Salt Cooled High Temperature Reactor (FHR) Raluca Scarlat, Per F. Peterson Department of Nuclear Engineering University of California, Berkeley TEA Conference, Washington, DC 12 May MWth, 410 MWe PB-AHTR

2 The PB-AHTR is a compact pool-type reactor with passive decay heat removal 2

3 Potential Benefits of Radially-Zoned, Annular Seed/Blanket Core Configuration Zoning allows use of thorium blanket pebbles External Pa-233 decay storage Closed and once-through seed-blanket fuel cycles being studied Effective neutron shielding of outer radial reflector Greatly reduced core pressure drop (using a combination of axial and radial flow) 3

4 Fluoride salt cooled High Temperature Rectors (FHRs) Combine Two Older Technologies Liquid fluoride salt coolants Excellent heat transfer Transparent, clean fluoride salt Boiling point ~1400ºC Reacts very slowly in air No energy source to pressurize containment But high freezing temperature (459 o C) And industrial safety required for Be Coated particle fuel (TRISO Fuel) FHRs have uniquely large fuel thermal margin 4

5 Reactor Safety: PB-AHTR Defense in Depth TRISO Particles Micro-containment vessels (>10,000 per fuel element) HVAC Zones 1 - Reactor cell (Low-Leakage Inerted Containment) 2 - Reactor citadel (Filtered Confinement) 3 Reactor quipment hallways (Ambient air) 4 - Turbine hall (Ambient air) additional hold-up 5

6 Modular PB-AHTR Economics Much more compact equipment than Gas Cooled Reactors 900 MWth PB-AHTR 400 MWth PBMR 6 1. D. T. Ingersoll, et al., "Status of Preconceptual Design of the Advanced High- Temperature Reactor (AHTR)," ORNL/TM-2004/104, pp. 69, 2004.

7 PB-AHTR Materials Metallic components ASME Section III alloys include 316 SS, Hastelloy N, Alloy 800H» 316 SS (high neutron tolerance, well developed code case for up to 800 o C, low corrosion with clean flibe & Be metal redox control, additional corrosion testing needed)» Hastelloy N (lower neutron tolerance, incomplete code case, excellent corrosion performance, higher cost) Reflectors are graphite Compatibility with fluoride salts excellent Recent scoping experiment shows that fluoride salt can be an excellent lubricant for graphite pebbles sliding on graphite Carbon composite and/or SiC composites could also be valuable e.g., shut-down rod channel liners 7 Hastelloy N modified with 2% titanium shows excellent corrosion and neutron embrittlement resistance, The Development Status of Molten-Salt Breeder Reactors, ORNL-4812, pp. 205, August 1972.

8 PB-AHTR Development Program and Licensing Approach Viability phase --> Performance phase --> Demonstration phase 8

9 Licensing Framework Generating the Frenquency-Response Plot Example AOO Acceptable Example DBE Example BDBE 10-CFR CFR50.34 Isorisk line Unacceptable Latent QHO DOSE (TEDE REM) AT EXCLLUSION AREA BOUNDARY (EAB) 9 Transient response codes must be validated against Separate Effect Test and Integral Effect Test experiments Understanding of plant transient response and resulting safety should be broadly based and non-proprietary

10 Licensing Framework Generating the Frenquency-Response Plot Example AOO Acceptable Example DBE Example BDBE 10-CFR50.20 Unacceptable 10-CFR50.34 Isorisk line Latent QHO DOSE (TEDE REM) AT EXCLLUSION AREA BOUNDARY (EAB) LBE frequency analysis depends upon slowly evolving phenomena Materials testing, component design and testing, and reliability engineering are critical in affecting event frequency and plant availability/economics Integrated design solutions that can demonstrate predictable and high reliability have commercial value (see NuScale example)

11 The FHR Development Program has three phases Viability Phase (nominally 3 to 4 years) Simulant Fluids SET and IET Experiments performed Major end products: Conceptual design for a 16-MWth Test Reactor NRC pre-application review submittal Performance Phase (nominally 4 years) Component Test Facility operates, and Fuel Qualification underway Major end products: Construction authorization for a 16-MWth Test Reactor Submittal of NRC Design Certification Application for a commercial prototype Demonstration Phase (nominally 5 years) 16-MWth AHTR Test Reactor operates Major end products: NRC Design Certification NRC Combined Construction and Operating License for a commercial-scale PB-AHTR Pilot Plant 11

12 Systematic Methodology for Guiding PB-AHTR Development The Role of Modeling and Experimentation System Design Construction System Model Dominant Phenomena Integral Effects Tests (IETs) Separate Effects Tests (SETs) 12 Characterization of Individual Phenomena

13 Systematic Methodology for Guiding PB-AHTR Development: Hierarchical System Decomposition 13

14 Major AHTR Experimental Program Elements 14 Integral Effects Tests Compact Integral Effects Test (CIET) facility» Scaled simulant fluid IET to study system response to LOFC, ATWS, and other transients Pebble Recirculation Experiment» Scaled simulant fluid IET to study pebble recirculation hydrodynamics Czech EROS zero power critical tests (w/ salt) (Viability phase)» Validate predictions for negative coolant void reactivity Separate Effects Tests Scaled High Temperature Heat Transfer (S-HT 2 ) facility» Heat transfer coefficient measurements using simulant fluids Fuel irradiation and post-irradiation examination Other SET experiments» Materials corrosion test loop» Pebble friction coefficients» Confirmatory data during component test experiments

15 Dowtherm A is a useful simulant fluid for fluoride salts Prandtl Number for flibe and Dowtherm A T melt, flibe T in T out T melt, Dowtherm 15 Dowtherm A is an excellent simulant coolant fluid for flibe molten fluoride salt.

16 Dowtherm A is a useful simulant fluid Results and Comparison of Dowtherm Data with Flibe Data ORNL flibe Pr Range ORNL flibe Re Range Turbulent Flow Correlations 16 ORNL FLiBe Correlation 4 < Pr < 14 S-HT 2 Correlation 8 < Pr < 36 Dowtherm A data matches available flibe data ORNL flibe data covers a narrower Pr range, and underestimates Nu at higher Pr Cooke J.W., Cox B. Forced Convection Heat Transfer Measurements with a Molten Fluoride Salt Mixture Flowing in a Smooth Tube. March Oakridge National Laboratory. ORNL-TM-4079.

17 Pebble bed dynamics modeling can be validated PREX 3.0 PREX 3.1 Suction Pebble injection Blowing Dry experimental/simulation demonstration for radially-zoned pebble 17 motion Wet experiment scaled to match Re and Fr

18 Availability of a simulant fluid reduces the size and cost of a IET Facility PB-AHTR CIET facility, 0.1MW, under construction at 1:1 effective height (1:2 actual) 1:190 effective power (1:9000 actual, 100 kw) reduced temperature / pressure small distortion from thermal radiation 18

19 Major AHTR Experimental Program Elements Component Tests Various scaled component tests with simulant fluids (water) Component Test Facility (CTF)» Major non-nuclear facility to test primary, intermediate and DRACS loop components under prototypical liquid salt conditions Test Reactor (DOE) nuclear fuel loading and pre-critical (zero power) testing low-power (<5%) testing and operation power ascension testing and operation not in excess of 100% interim operation maintenance and in-service inspection procedures Commercial Pilot Reactor (Industry) 19

20 Summary PB-AHTR Technology and the Path Forward AHTR achieves substaintial reduction in capital cost compared to ALWRs, primarily through compact size, no high pressure, and higher temperature/power conversion efficiency Excellent simulant fluids for molten fluoride salts allow for obtaining experimetal data at much lower costs than using prototypical fluids PB-AHTRs maintain uniquely large thermal margins for damage to fuel, and Coolant temperature limit is established by thermal limits on primary loop metallic structures Key issues relate to demonstrating predictable and high reliability, and confirming safety characteristics Development path involves pre-application review and subsequent Design Certification by NRC, and it has \clear roles for national laboratories, universities, and industry 20

21 Acknowledgements Professor Peterson s Research Group Tommy Cisneros neutronic analysis Mike Laufer pebble dynamics and hydrodynamics Cristhian Galvez, Nicolas Zweibaum thermal-hydraulic system modeling in RELAP5-3D Ed Blandford licensing methodology and passive shut-down rod hydrodynamics Lakshana Huddar, Jeff Bicket, AJ Gubser SET and IET experiments Minarets (tall towers) with small windows are used to allow for natural circulation cooling of buildings. This picture looks up into a minaret at Alhambra Palace, Granada, Spain (built in the 14 th century) 21

22 Now look, boys, I ain't much of a hand at makin' speeches, but I got a pretty fair idea that something doggone important is goin' on back there. And I got a fair idea the kinda personal emotions that some of you fellas may be thinkin'. [ ] I tell you something else, if this thing turns out to be half as important as I figure it just might be, I'd say that you're all in line for some important promotions and personal citations when this thing's over with. That goes for ever' last one of you regardless of your race, color or your creed. Now let's get this thing on the hump - we got some flyin' to do. (Dr. Strangelove, or How I Learned to Stop Worrying and Love the Bomb, 1964) 22

23 Back-up Slides 23

24 Construction of the Compact Integral Effects Test (CIET) Facility Facility Infrastructure Scaffold Equipment Support Rack Seismic Anchoring Key Components: Heater Element Facility Configuration Cooling Water and Drain Lines Drip Tray 24

25 25 The new UCB Compact Integral Effects Test (CIET) facility can be compared to the INL Semiscale facility Semiscale simulation of PWR LOCA 1:1 height 1:1705 flow area 1:1705 power (2 MW) 1:1 time prototype temperature / pressure CIET simulation of the PB-AHTR LOFC/ATWS 1:1 effective height (1:2 actual) 1:190 effective flow area (1:756 actual) 1:190 effective power (1:9000 actual, 100 kw) 1:(2) 1/2 time reduced temperature / pressure reduced heat loss small distortion from thermal radiation See for a list of other LWR IET s Semiscale, INL

26 Safety: AHTRs have unique defense in depth Ceramic TRISO fuel Over 500 C temperature margin to fuel failure under transients and accidents (unique among all solid-fuel reactor concepts) Immersion in chemically inert coolant with high fission product sorption capacity makes air/steam ingress impossible Negative coolant void/temperature reactivity feedback Passive natural-circulation decay heat removal Reactor cavity acts as a low-pressure, low leakage containment No stored energy sources to pressurize containment Large thermal inertia of cavity provides long time constant to primary coolant freezing Reactor citadel acts as a filtered confinement External event shell and turbine 26 hall provide additional hold up

27 With active-metal redox control, 316 SS has excellent compatibility with clean flibe 8 mm/yr 316 SS has excellent corrosion resistance with flibe with Be metal redox control 316 SS has an existing ASME Section III code case for use up to 800 C Issues include potential interactions with graphite surfaces in primary loop, and salt choice/corrosion control for intermediate loop (U. Wisc. experiments give 1.8 mm/yr 316 SS corrosion for KCl/MgCl 2 with Mg metal control) 27 J. R. Keiser, J. H. DeVan, and E. J. Lawrence, "Compatibility of Molten Salts with Type 316 Stainless Steel and Lithium," Journal of Nuclear Materials, pp

28 AHTRs use reduced salt conditions to maintain very low solubility for structural materials 28 AHTR s can use a corrosion resistant cladding (Hastelloy N or similar) with an ASME Section III code qualified structural material (e.g., Alloy 800H) Highly reduced conditions maintained by contacting salt with Be metal

29 Dowtherm heat transfer oil can be used as the principal simulant fluid for AHTR IET/SET experiments Scaling parameters to match Pr, Re, Gr, and Fr for flibe and Dowtherm A 29 Note that Pr, Re, Gr and Fr can be matched at < 2% of prototypical heater power Water can be used for hydrodynamics experiments